The four men -- Australian Shaun Davidson, Bulgarian Dimitar Nokolov, Indian Sayed Muhammed and Malaysian Tee Kok King -- escaped Sunday night by traveling through a waste tunnel from a prison clinic to an outside wall. Surung Pasaribu, chief of corrections on Indonesia's Bali island, said the 10 security guards on duty Sunday were questioned but there was no suspicion of their involvement in the jailbreak.

The escapees, serving time for drug, money laundering and passport fraud offenses, escaped through a 20-inch by 28-inch hole in a wall which connected to a narrow waste tunnel 50 feet long and less than 2 feet wide, officials said. The tunnel was drained Monday in the event any other escapees were confined in it.

Tonny Nainggolan, governor of the prison, said authorities were not aware that a cement cover in a wall hid the tunnel.

"We assumed it was the top of the septic tank because it was located next to the clinic toilet. It's been there for a while. We didn't suspect anything," Nainggolan said.

He added that 1,300 prisoners are incarcerated in the overcrowded jail.

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